






'''simple docstring'''




from math import factorial

def    __lowercase		(     __lowercase = 20			)			->		int:

      '''simple docstring'''


      _A     	=      2 * n  # middle entry of odd rows starting at row 3 is the solution for n = 1,
      # 2, 3,...
      _A     	=      n // 2

      return int(factorial(_lowerCamelCase			) / (factorial(_lowerCamelCase			) * factorial(n - k			))			)


if __name__ == "__main__":
    import sys

    if len(sys.argv) == 1:
        print(solution(20))
    else:
        try:
            lowerCamelCase_				   =   int(sys.argv[1])
            print(solution(n))
        except ValueError:
            print('''Invalid entry - please enter a number.''')













"""simple docstring"""





def 	lowerCamelCase__			(				_lowerCamelCase			:						str					) ->							bool:
  lowerCamelCase_       	=		0
  for ch in input_str:
    lowerCamelCase_       	=		ord(_lowerCamelCase					)
    lowerCamelCase_       	=		pow(2						,							_lowerCamelCase					)

    # If we already turned on bit for current character's unicode
    if bitmap >> ch_unicode & 1 == 1:
      return False
    bitmap |= ch_bit_index_on
  return True


if __name__ == "__main__":
  import doctest

  doctest.testmod()




